<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
    function Person(name,sex) {
        this.name = name;
        this.sex = sex
    }
    Person.prototype.extend = function (obj){
        for (var k in obj){
            this[k]=obj[k];
        }
    }

    function Student(num) {
        this.num =num;
    }
    Student.prototype = new Person('jack','男');

    var stu = new Student('001');
    console.log(stu);
    
    </script>
</body>
</html>